In security-critical environments, data frequently need to be sent redundantly or physical variables need to be measured and sent redundantly. Redundancy is necessary only in the event of error, however, and normally doubles the resources used, e.g. network bandwidth.
Particularly in the case of fail-operational systems, for example steer-by-wire systems in motor vehicles, redundant units are installed that are each linked via a redundant communication system to a processing control unit, e.g. a central computer. As a result, e.g. a measured value, for example the actual steering angle, is redundantly captured and in each case redundantly transmitted, i.e. received on the central computer four times. If the measured values are data having a large bandwidth, such as images from a stereo camera or radar echoes, then the quadrupling of the data has palpable effects on the network utilization level and network design. The larger dimensioning of the network has effects on unit cost, which is critical particularly in the automotive sector.
In this regard, a method is known according to which only one of the redundant nodes, what is known as the master, operates and sends data while the other, what is known as the slave, just monitors the function of the master and steps in in the event of error (absent or erroneous message). This involves the use of disjunct communication paths. It is possible for multiple slaves to be available for the same datum in order to further increase the reliability of the overall system.
Related approaches: High-availability Seamless Redundancy (HSR) defined in IEC 62439-3, an Ethernet protocol for filtering redundant messages in a ring. It does so by using tags on individual messages in order to recognize redundant transmissions without checking the content of the messages themselves.
Related approaches: in generally mesh networks, filtering is used in order to save bandwidth or to prevent the spread of undesirable content (Firewall). In this connection, there are related works in the field of wireless mesh networks, which are geared to reconfigurable networks with for the most part probabilistic approaches (cf. Mesh network firewalling with Bloom Filters, IEEE International Conference on Communications (ICC'07), 2007), however, these not being able to be used for the security-critical communication presented here.